1. Field of the Invention:
This invention relates to the field of solenoid operated valves and more particularly to an armature for a solenoid operated valve which has a seal component secured within a magnetically responsive tubular housing.
2. Description of the Prior Art:
Currently accepted designs of armatures for solenoid operated valves are represented pictorally in FIGS. 7p and 8p. The operation of solenoid operated valves is described in the Description of the Preferred Embodiment. FIGS. 7p and 8p illustrate the construction of currently accepted designs of armatures for solenoid controlled valves. Armature 55 consists of a solid cylindrical, magnetically responsive body 56 and a seal component 57. FIG. 7p illustrates a typical armature in which the seal component is a snap-on rubber seal, while FIG. 8p illustrates a typical armature in which the seal component is a recessed rubber seal.
Representative examples of variations and types of solenoid operated valves are disclosed by the following patent references:
______________________________________ Patent No. Patentee ______________________________________ 4,558,844 Donahue 4,387,878 Zukausky 4,174,824 Kolze 4,178,573 Swanson 4,175,590 Grandclement 3,872,878 Kozel et. al. 3,784,154 Ostrowski et. al. ______________________________________
The relevance of the above identified patents is limited to their disclosure of the environment in which the armature claimed herein will operate. Typical armatures used in the above disclosed patents are described hereafter.
One problem with currently accepted armatures which is apparent from FIGS. 7p and 8p is that expensive, close tolerance machining of expensive magnetic stainless steel is required in order to attach the seal component 57 securely to the magnetically responsive body 56. In order to maintain this close tolerance of machining, free machining magnetic stainless steels must be used in the magnetically responsive body 56. Free machining magnetic stainless steels are inherently less corrosion resistant than non-free machining magnetic stainless steels.
An additional problem with the armature illustrated in FIG. 8p is that a curling or staking operation is required in order to prevent the rubber seal from twisting during high pressure operation. Thus, should there be a failure of the connection of the seal component 57 to the body 56 in FIG. 8p, the seal component will become dislodged or twisted and therefore the sealing capability of the valve would be eliminated, leading to catastrophic flood and possible damage or personal injury.
As also illustrated in FIGS. 7p and 8p there is a spring guide member 58 located on the opposite end of armature 55 from seal component 57. Spring guide member 58 is also formed by machining the expensive magnetic stainless steel armature body. Since spring guide member 58 is formed of stainless steel, it should be apparent that spring guide member 58 could not sealingly engage a valve seat, thus requiring orientation of the armature during assembly of the solenoid operated valve. Critical assembly orientation greatly reduces the possibility of use of automated assembly methods for assembling the valves. This required orientation in assembly is an additional problem with currently accepted designs of armatures.
The presence of a metallic spring guide member on the opposite end of the armature from seal component 57 also increases the possibility of sharp impact between the metallic spring guide member 58 and the plastic closed end 48 (FIG. 1) of the guide tube when the solenoid is activated to move the armature 55 upwardly in the guide bore 11. This sharp impact between the metallic spring guide member 58 and the plastic closed end 48 of the guide tube may cause fracturing or knocking out of the guide tube. To reduce this effect, the guide tube must be extra long to provide a high degree of over travel for the current armature during operation. This is undesirable, since extra material must be used in the fabrication of the guide tube, and because even this does not completely solve the problem. Often a spring must be inserted in the guide tube to prevent plastic to metal impact.
Referring now more particularly to FIG. 8p, it should be apparent that there are other problems inherent in the recessed seal component design beyond merely the requirement of a critical curling (staking) operation to secure the seal component 57 in the magnetically responsive body 56. The recess seal component design requires critical alignment of the armature and valve seat during assembly. The recessed area for the rubber seal is surrounded circumferentially by the stainless steel body, thereby providing for a contact point between the soft plastic seat 30 and the stainless steel body during assembly of the valve. This results in a high probability of damage to the soft plastic seat by the armature which may affect the sealing capability of the valve. Thus, a critical alignment tolerance between the soft plastic seat and the recessed rubber seal must be maintained to prevent contact between the stainless steel armature recess curled diameter and the soft plastic seat. Not only must close tolerances be maintained in the curling operation of the armature but also the seat diameter is limited by the inside diameter of the curled portion of the armature body.
From the preceding it should be apparent that the inherent problems with the current designs of armatures for solenoid operated valves include:
(1.) Expensive close tolerance machining of expensive magnetic stainless steel is required;
(2.) Free machining magnetic stainless steels are inherently less corrosive resistant than non-free machining magnetic stainless steels;
(3.) A critical assembly operation (curling, staking) to prevent the rubber seal from pulling out or twisting during high pressure operation is required;
(4.) Orientation of the armature during assembly into the valve which complicates automated assembly procedures is required;
(5.) Since the armature body is of solid stainless steel and thus is relatively heavy, expensive solenoid coils must be used to overcome the gravitational force on the armature;
(6.) The possibility of damage to the soft plastic valve seats due to contact with the stainless steel armature is present;
(7.) Extra long guide tubes requiring extra material and springs are often required to prevent fracture and knocking out of the guide tube end by impact of the metallic end of the armature;
(8.) Critical alignment tolerances of the rubber seal to the soft plastic seat, and limitation of the seat diameter of the valve, must be maintained; and,
(9.) Because of the requirement of such close alignment between the valve seat and the seal, very little space for clearance of dirt or contaminated water between the armature and the bore of the guide tube is allowed with the recessed seal design.
Although the previous armature designs with a snap-on tip similar to that illustrated in FIG. 7p, overcome some of the problems with other previous armature designs, e.g. no critical assembly operation as described in 3 above is required and the critical alignment problem discussed in 8 above is overcome, the snap-on tip design has several inherent deficiencies which are overcome by the present invention. Among the deficiencies in snap-on tip armature designs which are overcome by the present invention are:
(1) During high pressure operation the snap-on tip in FIG. 7p may be pulled off while the seal in the present invention will remain in place: and,
(2) Even during low pressure operation, the rubber elastomer material used for the rubber tip in FIG. 7p can swell and degrade with use and therefore pull off, whereas the seal component in the present invention, if it does swell, will in fact become more firmly affixed within the armature body.
All of these disadvantages of currently accepted designs for armatures increase the costs of manufacturing, or reduce the efficiency of solenoid controlled valves. All of these problems are overcome by the preferred embodiment of the disclosed improved armature for solenoid operated valves.